Stabilized television circuit



Oct. 20, 1953 A. F. GIORDANOY 2,656,486

STABILIZED TELEVISION CIRCUIT Filed Sept. 28, 1950 ANTENNA SOUND SPEAKERCIRCUITS FRQg U E IQDY DEO C'RCUITS AMPLIFIER VERTICAL SYNC DEFLECTIONSENS/TOR CIRCUITS WAVE IN VEN TOR. AMER/C0 E GIORDANO A T TORNE YSPatented Oct. 20, 1953 UNITED STAT ACI'ENT F STABILIZED TELEVISIOIKTCIRCUIT America F Giordano; Newark, N, 1., assigno'r to Allen 15,.- Du-Mont Laboratories, Inc., Clifton, N'. J a corporation of Delaware-Applicaiion September 28, 1950,. Serial-No; 187,263

8 Claims. 1;

This invention relates to: television apparatus containing cathode-raytubes, and more. partic; ularly to meansfor: providing stabilized. focusandion trap adjustment. of such tubes.

In' the operation of a television receiver certain conditions arisesuchas, for instance, change in brightness level, which often causedefocusing and a necessity for readjustment of. the focus control.

An obiect of this. inventionis to provide stabilization in televisionreceivers.

A further obiectis to provide a circuit in which the focus a: televisionreceiver is. stabilized against changes in brightness of the picture;

Other objects are to provide Stabilization of focus and ion. trapadjustment against variations in the high voltage supply such as arecaused bythe a ineof tubes and the liker and against other. variationsof circuit elements during. the operation of a: television receiver,

In accordance: with the invention; the direct current which energizesthe focus coil is obtained from a portion of the circuit wherein voltageis dependent upon the operating condition of; the cathode-ray tube;,

The only figure of the drawing is a circuit dia-- gram of aatelevision'receiver, well known circuits being shown in block form andcircuits to which the present invention particularly relates bein shownschematic form.

An input winding H of a horizontal output transformer I2 is connected tothe anodes of a pair ofh'orizontal sweep amplifier tubes l3 and. M whichare connected to and driven by a signal source l'5 comprising ahorizontal deflections/ave generator; A' high voltagewindingl 6oft'h'e'h'orizontal output transformer H is connected" to a rectifierIT, which isin turn connected to a filter circuit to and through thistoan accelerating electrode I'QOf a picture tube 20. A secondary winding21 ofthe horizontal output transformer 12- is'c'on'nec'ted to a widthcontrol 22 and to a horizontal deflection coil 23'. A vertical"deflection coil 24 is connected in a well known manner to conventionalvertical deflection circuits. A linearity control 25 connects the inputwinding II and the secondary winding 2 I to a D. C. supply 26 of about350 volts through a damper tube 21, this circuit being well known.

An end 28 of the secondary winding 2| is connected to a shunt condenser29 and also to the vertical deflection circuits through a filter whichcomprises a series resistance 3| and a shunt capacitance 32, and to thehorizontal deflection wave generator through afilter which comprises 2;-seriesresistance 3-3 and ashunt capacitance 341 The said end 28 of thesecondary winding 2"l is also connected to a focus coil 36 through anaejustable focus control resistance 37, and toan ion trapcoil 38' throughan adjustable ion-trap control resistance 39. The focus coil- 36" andthe ion trap coil 38 are preferably electromagnetic. A- brightnesscontrol potentiometer 41* is connected-to the cathode of the picti-iretube 2-0 A resistor 4 having a" negativecoeflicient of resistance,isconnected inseries with the'focus coil 36 and positioned tobe-alfe'cted by heat therefrom. Thus focus coil current-is stabilizedwith respect to heating of the coil.

The operation of mostof the circuit-is well known. A drive wave 43supplied from the horizontal deflection wave generator [5- produces aperiodic current waveintlie horizontal sweep amplifier tubes l3' and I4. During the periods of time the tubes [3 and were out off; thevoltage4 at the plates of these tubes becomesm'cime'n tarily positive, chargingthe filter circui't It? to supply high voltageto the accelerating anodel9 of the picture tube 2-0'. A-boostervoltag'e'appears at the terminal:28 by virtue of the action-otthe damper tube 21 on the flyba'ck.energy,v charging the shunt condenser 29.--

In: the". preferred: embodiment oh the invention shown; current issuppliedto the vertical and horizontal-sweep" circuits:from the'boestedsource. Also currentziszsuppliedfromflthe 'boosted voltage source.to-theriocus cones: and ion: fil al-p 38 An exemplary means by whichthe invention accomplishes stabilization of focus isas follows-:

It. thei picture brightness i's increased,- as by adjustment otfthebriglitness control or change in .programzmaterial; the electron-beam orthe pic ture tube 20 draws more current fromtthe" high voltage supply,causing a reduction: in: the'zmagnitude'so'f the-high voltage: and:boosted voltage; the; exact amounts of voltage reduction beingdependentin part orttheregulation-of "the transfarmer The loweredvalueof highi voltage v'vhich thus occurs when the picture brightness isincreased, tends to cause defocusing because the electrons in the beammove more slowly and are overly deflected by the magnetic field producedby the focus coil 36. At the same time and in accordance with thisinvention, the focus coil current is reduced because the coil isconnected to the boosted voltage source. The reduced focus coil currentcauses a lowering of the intensity of the focusing magnetic field, sothat good focus of the electron beam is obtained at the new value ofaccelerating voltage. The focus-compensating change of current in thefocus coil occurs smoothly and continuously with ordinary changes in theaccelerating and boosting voltages. When a replacement picture tube isinstalled which, due to individual tube variances, has more or lesselectron beam current than the tube it replaces, the present inventionof stabilized focus will automatically provide focus coil currentcompensation in a manner as explained above.

The circuit disclosed in the present invention should provide focusstabilization when any operating condition arises that would tend tocause defocusing through a reduction of accelerating voltage due toregulation of the horizontal output transformer. vertical deflectioncircuits are compensated since these circuits are supplied powerfrom'the boosted voltage source. I

Although the preceding description has been directed to stabilization offocus, the invention is also adapted towards stabilization of an iontrap. In a bent gun system, the negative ions are trapped in an ion trapand the electrons are deflected by an ion trap magnet to pass out of theelectron gun toward the picture screen. The deflection of the electronsby the ion trap magnet is dependent upon the accelerating voltage. Ifthe electron speed becomes reduced due to a reduction in the magnitudeof accelerating voltage, the electron beam will tend to become overlydeflected by the ion trap magnet. To compensate for this efiect, the iontrap magnetic field must be reduced.

In accordance with my invention, the current in the ion trap magnet coil38 is reduced or increased along with a reduction or increase of thespeed of the electron beam, in a manner previously described in relationto the focus coil 36. The invention thus accomplishes stabilization ofan ion trap, in addition to stabilization of focus.

Also, changes in the horizontal and 1 3. In a television receiver, thecombination of a pulse source, a transformer connected thereto, acathode ray tube having an anode, means for deriving a voltage for saidanode from said transformer, a direct voltage source coupled to saidtransformer, and a rectifier connected to said transformer and saiddirect voltage source to produce a source of boosted direct voltage, anda focus coil connected to said source of boosted direct voltage.

4. In a television receiver, a cathode ray tube comprising an anode, adeflection transformer comprising a primary winding, a high voltagewinding connected to supply voltage to said anode, and an outputwinding; a source of signals connected to said primary winding; a focuscoil; and a series circuit comprising said coil, one end of said seriescircuit being connected directly to Although specific embodiments havebeen shown and described, the scope of the invention is defined in thefollowing claims.

What is claimed is:

1. In a television receiver,. a cathode ray pic- .ture tube having ananode and an electron beam subject tovariations, a first source ofpotential connected to saidanode and a second source of potentialconnected to said first source, both said potentials being subject tovariations in, accordance with variations of said electron beam'and anelectromagnet positioned adjacent said tube and-having an externalmagnetic field extending within said tube to influence said electronbeam, said electromagnet being connected to said second source. I

2. In a television receiver, a cathode tube havin an anode, a source ofelectrical pulses,- a transformer connected thereto, a rectifierconnected between said transformer and said anode, and a focus coil.connected to said transformer to derive operating voltage therefrom.

.1 said output winding.

5. In a television receiver having a cathode ray .tube containing ananode, a source of electrical pulses, a transformer, a primary windingand a secondary winding on said transformer, an electrical connectionbetween said source of electrical pulses and said primary winding, adeflection coil electrically connected to said secondary winding, arectifier connected to provide voltage to said anode from saidtransformer, a filter circuit connected to said secondary winding, and afocus coil electrically connected to said filter circuit.

6. The apparatus of claim 5, including an ion trap coil electricallyconnected to the said filter References Cited in the file of this patentUNITED STATES PATENTS Number Name Date 2,219,194 Mynall Oct. 22,1940 12,255,485 Dome Sept. 9, 1941 2,291,682 Blumlein et al Aug. 4, 19422,430,331 Galella et a1. Nov. 4, 1947 12,438,359 Clapp Mar. 23, 19482,443,030 Foster June 8, 1948. 2,447,804 Holst "Aug. .24, 1948 2,451,641Torsch Oct. 19,1948 2,512,779 Sherwin et al June 27, 1950 2,555,147Meagher May 29, 1951

